This invention relates to drinking glasses provided with means for thermally insulating their contents and capable of being chilled, more specifically suitable for being cooled down to at least -20.degree. C. or less.
There exist several reasons, in other words the applications, why the need is felt for pre-chill drinking glasses and with good thermal insulation: it is desired, in some instances, to prevent the formation of condensation on the walls whenever a cold drink happens to be contained in such glasses; it is desired not to warm up the contents of a glass held in the hand; it is desired to preserve contents at a given temperature, suitable for drinking it; or, furthermore, it is desired to cool the poured drink, by using the pre-chilling of the glass, so as to avoid dilution of the drink contents through the addition of ice by mentioning just a few examples.
The glass of the invention is of a type that may be pre-chilled in order to cool a drink and preserve it cold for a given time.
The advantages which are inherent in the procedure of chilling the glass for certain drinks which are recommended or preferred for use at a given temperatures ranging from 12.degree.-14.degree. C. for wines such as Bordeaux, to 4.degree. C. for some dry spirits, such as whisky, have already been fully realized since long. These reside, in addition to the fact that the drink remains undiluted, also in the capability presented by a chilled glass of cooling its contents down to a predetermined temperature whereat such contents is then maintained for a while, whereas, by using ice, the drink would continue to cool down, far below the desired temperature, as well as to dilute.
As early as 1947, E. L. Smith in his U.S. Pat. No. 2,526,165, and as 1948, T. P. Landers in his U.S. Pat. No. 2,622,415, proposed separately glasses which were suitable for pre-chilling, and thus for transferring a given amount of calories from the drinks poured thereinto. Both inventions provide glasses having walls formed with a hollow space wherein a liquid, e.g. water, is sealed which freezes at a moderately low temperature and is capable of yielding and absorbing appreciable amounts of heat during the phase conversion step.
The above cited inventions, which met with a good success, have, however two noteworthy practical drawbacks. First is in fact, the very presence of the phase-changing liquid, which constitutes their most advantageous thermal feature, with a high thermal capacity in a limited space, creates technological problems in that the change of phase implies substantial volume changes, and stresses that tax heavily the vitreous material typical brittleness, thereby their construction becomes difficult and costly to put into practice, if predetermined thermal expansions and thermal gradients are to be achieved. The second main drawback comes from the lack of a suitable thermal insulation from the ambient in such glasses. This results in a disagreable cold feeling being transmitted through the hand while the glass is held in the user's hand, and in the subtraction of part of the cold intended for chilling the drink, thereby the cooling effectiveness of such a container is reduced.
Indeed, glasses are known which have been provided with an improved thermal insulation of the contents from the surrounding space. The invention by B. P. Murphy (U.S. Pat. No. 2,832,493 issued in 1956) provides a duplex or dual type of drinking glass comprised of two containers, adapted for insertion one within the other and forming a hollow space therebetween. The object specified for this combination was to prevent condensation along the glass walls and avoid the cooling of the user's hand holding the glass.
Back in 1936, W. A. Morton disclosed in his U.S. Pat. No. 2,169,426 a glass comprising two cups, to be placed one within the other with a gap therebetween: however the object here was primarily of an aesthetic nature, since the two cups were respectively of a vitreous and metal material, playing with the color combinations thereof. The outer cup also performed a protective function, being preferably metallic, but provided no thermal insulation, since the inner cup extended for a considerable length not screened.
Furthermore, hot drink glass cups, such as coffee cups, provided with a vacuum interspace, "thermos" bottle fashion, effective to keep a drink hot for a considerably long time, are well known and currently being used for bar serving, for example, company offices.
Still another vessel, thermally insulated by an interspace also applicable to a drinking glass configuration, is disclosed in the U.S. Pat. No. 3,221,915 issued in 1962 to W. J. Gort; therein the inner wall is made of glass or a vitreous matter, and an outer one is made of plastics; the interspace is filled with a foamed or expanded resin effective to provide thermal insulation and shock resisting properties.
It might appear obviously expedient to combine a drinking glass having a two-phase coolant of the type described above with a thermal insulation according to either one of the cited methods. However the problem is not so simple, and although the need for such a drinking glass is definitely felt, it has not been as yet fulfilled. In fact, the addition of a second interspace would make the glass, which already comprises a hollow interspace, exceedingly thick and difficult to manufacture. Thus different approaches have been considered in other directions and for special objects.
H. G. Zimmerman proposes, in his U.S. Pat. No. 2,876,634 of 1954, a coffee cup, easily adaptable to produce a drinking glass, containing a "thermodynamic" liquid which changes phase when placed into a refrigerator, under the effect of a hot drink, such as coffee, to stop its cooling at a desired temperature.
Similarly to Zimmerman's teachings, but in an even simpler manner, G. P. Todd in his U.S. Pat. No. 3,766,975 provides water in the interspace of a coffee cup, not freezable, effective to rapidly cool its coffee contents based upon the thermal masses and specific heat ratios involved, and keep it for a few minutes within a desired temperature range, thanks to the increased overall thermal mass.
Thus, the general problem has been left largely unsolved of providing a drinking glass capable of cooling a drink poured thereinto.